Banned? why?

I was playing Halo Reach and while I did play match making a lot today, i decided to join Custom Games. While in custom games or 30 mins, twice a screen msg popped up saying that I was banned from earning credits. Why and for how long this time again? last time i got banned was when I went AFK 3 times in a row during Griffball matches because they are quick games and sometimes your avatar stays in the queue with the rest. I understand that ban. So, how long now and for what reason? I am so fricken close to Noble rank. This is totally frusterating. plz respond!

Post in the Why am i banned threadhttp://halo.xbox.com/Forums/yaf_postst20947_Why-Did-I-Get-Banned–The-Official-Thread.aspx

2nd time ban is 2 weeks long, allso post your GT so people can look in to what you did wrong. 0 kills in matches will get you cR banned.